This proposal aims to extend, to Brazil, studies on high risk behavior and HIV-1 infection among drug abusers. The current work has been in progress for 5 years in Philadelphia, and this proposal requests three years of funding to study the spread of HIV- 1 in Brazil among 400 persons who meet DSM-IV criteria for dependence on cocaine, opioids, or polysubstance dependence. 200 subjects will be recruited at two sites in Brasilia beginning in year 1, and an additional 200 ss will be recruited from two sites in Porto Alegre beginning in year 2. Subjects will be assessed at baseline and every six months over an 18 month period (total of 4 assessment points) for drug use patterns, AIDS risk behavior, infection with HIV-1, and psychiatric symptoms using measures that have been used in Philadelphia. Final data analyses will be done in Philadelphia after data entry in Porto Alegre. This work will be carried out through a collaboration between investigators at the University of Pennsylvania (Drs. Woody, Metzger), the Federal University of Rio Grande do Sul (Drs. Pechansky, Soibelman), and the Federal University of Brasilia (Dr. Sudbrack). Its aims are to: 1) Adapt research measures that have been used successfully among drug abusers in Philadelphia and other parts of the U.S. to Brazilian culture 2) Assess group characteristics in terms of sociodemographic variables and psychiatric symptoms among subjects in Brasilia and Porto Alegre 3) Determine drug use patterns and risk behaviors among individuals who are either IDU's, or drug users with multiple sexual partners or other behaviors that put them at risk I-or HI"" infection 4) Determine the prevalence and incidence of HI"" infection at baseline and at 6, 12 and 18 months among subjects recruited at each of the two sites in Brasilia and Porto Alegre 5) Determine the proportion of subjects who do not have the necessary reading skills to fill out self-reported questionnaires, and assess whether these subjects differ from other subjects on major study variables 6) Compare data obtained from Brazil with that obtained in Philadelphia over a similar period of time 7) Determine the viability of building a long-term collaboration between the Brazilian study sites and the University of Pennsylvania for future studies of HIV among drug abusers.